Multi-Phase Pump

ABSTRACT

A multi-phase pump for the pumping of mixtures, which contain a plurality of phases is proposed. The multi-phase pump ( 1 ) is equipped with at least one rotor ( 5.1, 5.2 ), a hollow shaft ( 2 ) on which the rotor is arranged and with at least one shaft extension piece ( 10 ) which respectively includes a shaft extension ( 12, 12.2 ) with a shaft diameter which is smaller relative to the hollow shaft and a connection part ( 11 ), in order to connect the at least one shaft extension piece to the hollow shaft. Additionally a flange ( 11   a ) is formed on the connection part ( 11 ) of the shaft extension piece ( 10 ), which is connected to an end face ( 2   a ) of the hollow shaft ( 2 ).

The invention relates to a multi-phase pump in accordance with the pre-characterising part of claim 1 for the pumping of mixtures, which contain a plurality of phases.

In the pumping of mixtures, which contain a plurality of phases, such as raw oil for example, which in addition to crude oil also contains natural gas and also water and often solid components, such as sand for example, the problem arises that, as the proportion of gas increases in the mixture, the degree of efficiency of the pumping devices with radial rotors decreases. For example, at lower gas concentrations, the use of pumping devices with radial rotors is no longer possible or economical once there is a volumetric gas/liquid ratio of more than 0.04 to 0.06. For this reason special multi-phase pumps are used for mixtures with an elevated proportion of gas. A multi-phase pump is described in the document GB-A-1 561 454 for example. It contains a helical-axial rotor with a hub and at least one blade fastened to the same. The blade has a profile which is formed by the intersection of the same with the surface of a cylinder which is coaxial to the rotor, with the angle of inclination of the profile to the axial direction continually decreasing from the leading edge of the blade to the trailing edge. Essentially, the profile does not have any curvature in the immediate vicinity of the leading edge, with the steepness of a curve of the blade profile curvature increasing constantly as a function of the axial spacing from the leading edge with increasing distance from the leading edge.

The rotors of multi-phase pumps typically have a comparatively large internal diameter (see FIGS. 2A and 2B of GB-A-1 561 454 for example). Therefore, for reasons of rotor dynamics, hollow shafts are mainly required, since the lower mass of the hollow shafts increases the natural frequency and the limit to instability. Due to the large internal diameter of the rotors, the hollow shaft is normally provided with shaft extensions, which have a smaller diameter, so that the bearings and the seals, which seal the shaft extensions relative to the pump housing, can be made smaller.

In the described embodiment the shaft extensions have to be connected to the hollow shaft. For this purpose the shaft extensions, which were previously designed as shaft spigots were shrunk into the hollow shaft with simultaneous axial abutment of the shaft spigot in the hollow shaft. With the shrunk connection problems with the stability of the connection repeatedly arose. These are due, on the one hand, to the material used for the shaft (austenitic steel or duplex steel), with which a creeping of the material under the constant load of the shrunk connection and thus a loosening of the connection can not be ruled out. On the other, hand the problems are caused by manufacturing difficulties. Tolerances and a non-uniform cooling over the periphery can lead to a non-uniform shrunk connection with reduced load capacity. A further disadvantage of the shrunk connection is the insufficient sealing of the hollow shaft relative to the mixture to be pumped. The advantage of the lower mass can be negated, at least in part, by the infiltration of liquid into the hollow shaft.

It is the object of the invention to make available a multi-phase pump with a hollow shaft, which is provided with shaft extensions, which are connected to the hollow shaft in stable manner and which can be simply sealed relative to the hollow shaft.

This object is satisfied by the multi-phase pump defined in claim 1.

The multi-phase pump in accordance with the invention for the pumping of mixtures, which contain a plurality of phases, includes at least one rotor, a hollow shaft on which the rotor is arranged and at least one shaft extension piece, which respectively includes a shaft extension with a shaft diameter which is smaller relative to the hollow shaft and a connection part, in order to connect the at least one shaft extension piece to the hollow shaft. In addition a flange is formed on the connection part of the shaft extension piece, which is connected to an end and/or end face of the hollow shaft. The flange formed on the connection part can be connected to one of the ends and/or end faces of the hollow shaft by means of a plurality of screws and/or threaded bolts for example.

In a preferred embodiment the multi-phase pump includes on one side of the hollow shaft a shaft extension piece with a shaft extension and a connection part on which a flange is formed, which is connected to an end and/or end face of the hollow shaft and, on the other side of the hollow shaft, a shaft extension formed directly on the same with a smaller shaft diameter relative to the hollow shaft.

In a further preferred embodiment the multi-phase pump includes two shaft extension pieces each with a connection part on which a flange is formed, which is respectively connected to an end and/or an end face of the hollow shaft.

In an advantageous embodiment the shaft extension piece or pieces each include one or more centering elements in order to center the shaft extension piece or pieces relative to the hollow shaft. The centering element or pieces can, for example, project into the hollow shaft, with the shaft extension piece or pieces being able to be centered, if required, on an inner side or inner surface of the hollow shaft.

In a further preferred embodiment a seal, for example an o-ring seal, is respectively provided between the shaft extension piece or pieces and the hollow shaft in order to seal the shaft extension piece or pieces relative to the hollow shaft.

Independently of the embodiment the multi-phase pump can, if required, include one or more bearings, for example one or more radial bearings and/or axial bearings in order to rotatably journal the shaft piece or pieces, and/or a pump housing and one or more seals, for example one or more rotary seals to seal the shaft extension piece or pieces relative to the pump housing.

The multi-phase pump in accordance with the invention has the advantage that a secure connection between the shaft extension piece and the hollow shaft is guaranteed by the flange mounting of the shaft extension piece at an end and/or an end face of the hollow shaft. The attachment of the shaft extension by a flange enables, in addition, a simple seal between the shaft extension and the hollow shaft, for example with the help of an o-ring seal.

The above description of embodiments and variants merely serves as an example. Further advantageous embodiments are documented in the dependent claims and the drawing. Furthermore within the context of the present invention individual features from the described or illustrated embodiments and variants can also be combined with one another in order to form new embodiments.

The invention will be described in more detail in the following with the help of the drawings which show:

FIG. 1 an embodiment of a multi-phase pump in accordance with the present invention, and

FIG. 2 a detailed view of the shaft connection from the embodiment of FIG. 1.

In the embodiment shown in FIG. 1 and FIG. 2 the multi-phase pump 1 for the pumping of mixtures which contain a plurality of phases, is equipped with at least one rotor 5.1, 5.2, a hollow shaft 2 on which the rotor is arranged and at least one shaft extension piece 10. The shaft extension piece 10 includes a shaft extension 12, 12.2 with a shaft diameter which is smaller relative to the hollow shaft and a connection part 11, in order to connect the at least one shaft extension piece to the hollow shaft. A flange 11 a is additionally formed at the connection part 11 of the shaft extension piece 12.12.2, which is connected to an end and/or end face 2 a of the hollow shaft 2. The end face can, for example, as shown in the FIGS. 1 and 2, include the entire end or only a part of the same. It is, however, also possible to arrange the end face recessed in the hollow shaft. The rotor or rotors 5.1, 5.2 advantageously each include one or more blades, which can have an inlet angle between 2° and 50° for example, in particular between 4° and 25° and an outlet angle which can lie between the inlet angle and 60° for example, in particular between the inlet angle and 25°. The outer diameter of the flange 11 a can, as shown in the FIGS. 1 and 2, be selected to be essentially equal in size to the outer diameter of the hollow shaft 2. It is, however, if required, also possible to select the outer diameter of the flange to be larger or smaller than the outer diameter of the hollow shaft 2. If necessary, a pressure element, for example a pressure plate can be provided, with which the flange can be pressed against an end face of the hollow shaft. This is in particular advantageous when the outer diameter of the flange is smaller than the outer diameter of the hollow shaft. Independently of this, an outer diameter larger relative to the rest of the hollow shaft and/or a flange can be provided on the hollow shaft at least at one end. This is particularly preferable when the hollow shaft is made comparatively thin-walled and the strength of the connection between the flange 11 a of the connection part 11 and one of the ends and/or end faces 2 a of the hollow shaft is critical.

The flange 11 a formed on the connection part 11 can, for example, be connected to one of the ends and/or end faces 2 a of the hollow shaft by means of a plurality of screws and/or threaded bolts 13.1, 13.2. If a pressure element, for example a pressure plate, is present with which the flange 11 a of the connection part can be pressed against an end and/or end face of the hollow shaft, the pressure element can be connected to one of the ends/and or end faces 2 a of the hollow shaft by means of screws and/or threaded bolts 13.1, 13.2.

In an advantageous embodiment the multi-phase pump includes two shaft extension pieces 10 each with a connection part 11, on which a flange 11 a is formed, which is respectively connected to an end and/or an end face 2 a of the hollow shaft 2. It is however also possible, as shown in FIG. 1, to attach a shaft extension piece 10 with a shaft extension 12.2 only to one end of the hollow shaft 2 and to provide a shaft extension 12.1 at the other end which is formed directly on the hollow shaft with a shaft diameter which is smaller relative to the hollow shaft.

In an advantageous embodiment the shaft extension piece 10 respectively includes one or more centering elements 11 b, in order to center the shaft extension piece relative to the hollow shaft 2. The centering element or pieces can project into the hollow shaft for example, and the shaft extension piece can, if required, be centered on an inner side or inner surface 2 b of the hollow shaft 2. If necessary fine machining can be provided for the inner side or inner surface 2 b of the hollow shaft, for example in that the inner side or inner surface is additionally turned, in order to guarantee a perfect centering of the shaft extension piece. A short centering bolt can, for example, be provided as a centering element, as shown in FIGS. 1 and 2, which is fitted into the hollow shaft.

In further advantageous embodiment a seal 14 is respectively provided between the shaft extension piece or pieces 10 and the hollow shaft 2 in order to seal the shaft extension piece or pieces relative to the hollow shaft. The seal can, for example, as shown in FIG. 2, be provided between the centering element 11 b and the inner side or inner surface 2 b of the hollow shaft 2, or additionally or alternatively between the flange 11 a of the connection part 11 and one of the ends and/or end faces 2 a of the hollow shaft. If the seal is provided between the centering element 11 b and the inner side or inner surface 2 b of the hollow shaft, then a fine machining of the inner side or inner surface, as has already been described in connection with the centering of the shaft extension piece, is advantageous to improve the seal. Comparatively inexpensive elastomeric seals, such as o-ring seals for example, can be used as seals, since the temperature at the sealing point is limited and normally lies below 100° C. both during manufacture and in operation.

Independently of the embodiment the multi-phase pump 1 can occasionally include one or more guide elements 4.1, 4.2. A guide element 4.1, 4.2 is advantageously respectively provided after a rotor 5.1, 5.2, which forms a pumping and/or compression stage together with the preceding rotor. The multi-phase pump can include one or more stages, for example four stages as shown in FIG. 1. In the longitudinal section shown in FIG. 1, rotors and guide elements are each only drawn in the upper part of the shown multi-phase pump, whereas in the lower part the corresponding axially symmetrically pictures of the rotors and the guide elements were left out.

In an advantageous embodiment the multi-phase pump optionally includes one or more bearings, for example one or more radial bearings 9.1., 9.2 and/or axial bearings 9.3, in order to rotatably journal the shaft extensions 12.1, 12.2, and/or a pump housing 3 and one or more seals, which are not shown in FIG. 1, for example one or more slide ring seals, restrictor gaps with labyrinths, restrictor gaps with radial sealing rings, with quench seals, floating ring seals, brush seals or packings, in order to seal the shaft extensions 12.1, 12.2 relative to the pump housing 3. The pump housing 3 is typically provided with an inlet 7 and an outlet 8.

The described multi-phase pump for the pumping of mixtures, which contain a plurality of phases, makes a stable operation possible thanks to the hollow shaft, even with a large internal diameter of the rotors and makes the use of bearings and seals with a reduced diameter relative to the hollow shaft possible, thanks to the shaft extension piece or pieces, which has a positive effect on both the manufacturing costs and the servicing costs. The flanging of the respective shaft extension piece to an end face of the hollow shaft further makes possible a secure connection and a simple sealing between the shaft extension piece and the hollow shaft. 

1. A multi-phase pump for the pumping of mixtures, which contain a plurality of phases, having at least one rotor (5.1, 5.2), a hollow shaft (2) on which the rotor is arranged and at least one shaft extension piece (10) which respectively includes a shaft extension (12, 12.2) with a shaft diameter which is smaller relative to the hollow shaft and a connection part (11), in order to connect the at least one shaft extension piece to the hollow shaft, characterised in that a flange (11 a) is formed on the connection part (11) of the shaft extension piece (10), which is connected to an end and/or end face (2 a) of the hollow shaft (2).
 2. A multi-phase pump in accordance with claim 1 including, at one end of the hollow shaft (2), a shaft extension piece (10) with a shaft extension (12.2) and a connection part (11) on which a flange (11 a) is formed, which is connected to an end and/or to an end face (2 a) of the hollow shaft and, at the other end of the hollow shaft, a shaft extension (12.1) formed directly on the same with a smaller shaft diameter relative to the hollow shaft.
 3. A multi-phase pump in accordance with claim 1 including two shaft extension pieces (10) each with a connection part (11) on which a flange (11 a) is formed, which is respectively connected to an end and/or an end face (2 a) of the hollow shaft (2).
 4. A multi-phase pump in accordance with claim 1, wherein the shaft extension piece or pieces (10) each include one or more centering pieces (11 b) in order to center the shaft extension piece or pieces relative to the hollow shaft (2).
 5. A multi-phase pump in accordance with claim 1, wherein the centering element or pieces (11 b) project into the hollow shaft (2), in particular in such a way that the shaft extension piece or pieces (10) are centered on an inner side or inner surface (2 b) of the hollow shaft.
 6. A multi-phase pump in accordance with claim 1, wherein a seal (14) is respectively provided between the shaft extension piece or pieces (10) and the hollow shaft (2) in order to seal the shaft extension piece or pieces relative to the hollow shaft.
 7. A multi-phase pump in accordance with claim 1, wherein the flange (11 a) formed on the connection part (11) is respectively connected to one of the ends and/or end faces (2 a) of the hollow shaft by means of a plurality of screws and/or threaded bolts (13.1, 13.2).
 8. A multi-phase pump in accordance with claim 1 additionally including one or more bearings (9.1, 9.2, 9.3) to rotatably journal the shaft extension or extensions (12, 12.1, 12.2).
 9. A multi-phase pump in accordance with claim 1 including a pump housing (3) and one or more seals in order to seal the shaft extension or extensions (12, 12.1, 12.2) relative to the pump housing. 